Cosmo,
Don't know what's been happening, this is the third time I have tried to post to you. Just wouldn't do it.
Very strange, I ran a Celeron 400mhz with 128mb of RAM and G400 16mb card. I changed to 533mhz yesterday.
I am thinking that your RAM might be stalling. Your PIII 600 runs at 100mhz and your RAM at 133mhz, it should be OK but it is also possible that it could slow down. You should also get the latest drivers from Matrox, they have had 4 sets in the past 3 months. What you want is w9x522. You will also need their uninstaller to remove the current drivers. This very important. Install the new ones and don't get alarmed when you lose your colours. Just follow the sequence.
Download from Microsoft DIRECTX7a - this too is important. DX8 is due out shortly.
Check that your AGP aperture setting in BIOS is set at 64mb, exactly half of the RAM. Some set it per the RAM but it can cause serious problems later. Also check at the motherboard site if their is a flash update.
Try it anyway - it will keep you busy for a while. You can e-mail me if you wish - no problem.
I would like to know if it works anyway.